Maybe I’m wrong, but it would be a surprise unless facing his mortality makes Mr. Gold desperate enough to think two muggles can take on powerful witches.
But did he expect that they’d have to take them on? The whole purpose of the Charmings finding the dagger wasn’t so they could use it to confront anyone, it was so Cora and Regina wouldn’t find it. The Charmings getting it first was meant to eliminate the threat of anyone wreaking havoc with it. It’s just that Cora and Regina were onto them, and the plan to keep the dagger out of their hands ended up being a bust.